Triggering an update on a second table after insert
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0
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I have two tables, A and P.
A
________________
id | num_cars
----------
1 | 2
2 | 0
3 0
P
__________________________
id_driver | id_car
--------------------------
1 | Porsche
1 | BMW
A.id and P.id_driver referes to the same person. I created the below trigger. The idea is, every time I add a new row in P for an existing driver its correspondent row in A must be updated with the number of total cars owned by the person with that id.
CREATE OR REPLACE FUNCTION update_a() RETURNS trigger AS $$
BEGIN
IF TG_OP = 'INSERT' THEN
UPDATE A a
SET num_cars = (SELECT COUNT(NEW.id_driver)
FROM P p
WHERE (a.id = p.id_driver AND a.id=NEW.id_driver));
ELSIF TG_OP = 'DELETE' THEN
UPDATE A a
SET num_cars = num_cars - 1
WHERE a.id = OLD.id_driver AND a.num_cars<>0;
END IF;
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER add_car
AFTER INSERT OR DELETE ON PARTICIPATION
FOR EACH ROW EXECUTE PROCEDURE update_a();
The trigger works fine when I add a row in B for a driver. However, if I then add a row for a different driver in B the rest of the rows in A are set back to 0. I would like the procedure to run only when A.id = P.id_driver. How can I do this?
postgresql postgresql-9.1 postgresql-9.3
asked Nov 20 at 12:54
Sergio
164
add a comment |
up vote
0
down vote
favorite
I have two tables, A and P.
A
________________
id | num_cars
----------
1 | 2
2 | 0
3 0
P
__________________________
id_driver | id_car
--------------------------
1 | Porsche
1 | BMW
A.id and P.id_driver referes to the same person. I created the below trigger. The idea is, every time I add a new row in P for an existing driver its correspondent row in A must be updated with the number of total cars owned by the person with that id.
CREATE OR REPLACE FUNCTION update_a() RETURNS trigger AS $$
BEGIN
IF TG_OP = 'INSERT' THEN
UPDATE A a
SET num_cars = (SELECT COUNT(NEW.id_driver)
FROM P p
WHERE (a.id = p.id_driver AND a.id=NEW.id_driver));
ELSIF TG_OP = 'DELETE' THEN
UPDATE A a
SET num_cars = num_cars - 1
WHERE a.id = OLD.id_driver AND a.num_cars<>0;
END IF;
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER add_car
AFTER INSERT OR DELETE ON PARTICIPATION
FOR EACH ROW EXECUTE PROCEDURE update_a();
The trigger works fine when I add a row in B for a driver. However, if I then add a row for a different driver in B the rest of the rows in A are set back to 0. I would like the procedure to run only when A.id = P.id_driver. How can I do this?
postgresql postgresql-9.1 postgresql-9.3
asked Nov 20 at 12:54
Sergio
164
Maybe because you're callingupdate_carin your trigger and notupdate_aor is that a typo?
– Joakim Danielson
Nov 20 at 13:33
I've corrected the typo, sorry for the confusion
– Sergio
Nov 20 at 15:29
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I have two tables, A and P.
A
________________
id | num_cars
----------
1 | 2
2 | 0
3 0
P
__________________________
id_driver | id_car
--------------------------
1 | Porsche
1 | BMW
A.id and P.id_driver referes to the same person. I created the below trigger. The idea is, every time I add a new row in P for an existing driver its correspondent row in A must be updated with the number of total cars owned by the person with that id.
CREATE OR REPLACE FUNCTION update_a() RETURNS trigger AS $$
BEGIN
IF TG_OP = 'INSERT' THEN
UPDATE A a
SET num_cars = (SELECT COUNT(NEW.id_driver)
FROM P p
WHERE (a.id = p.id_driver AND a.id=NEW.id_driver));
ELSIF TG_OP = 'DELETE' THEN
UPDATE A a
SET num_cars = num_cars - 1
WHERE a.id = OLD.id_driver AND a.num_cars<>0;
END IF;
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER add_car
AFTER INSERT OR DELETE ON PARTICIPATION
FOR EACH ROW EXECUTE PROCEDURE update_a();
The trigger works fine when I add a row in B for a driver. However, if I then add a row for a different driver in B the rest of the rows in A are set back to 0. I would like the procedure to run only when A.id = P.id_driver. How can I do this?
postgresql postgresql-9.1 postgresql-9.3
asked Nov 20 at 12:54
Sergio
164
I have two tables, A and P.
A
________________
id | num_cars
----------
1 | 2
2 | 0
3 0
P
__________________________
id_driver | id_car
--------------------------
1 | Porsche
1 | BMW
A.id and P.id_driver referes to the same person. I created the below trigger. The idea is, every time I add a new row in P for an existing driver its correspondent row in A must be updated with the number of total cars owned by the person with that id.
CREATE OR REPLACE FUNCTION update_a() RETURNS trigger AS $$
BEGIN
IF TG_OP = 'INSERT' THEN
UPDATE A a
SET num_cars = (SELECT COUNT(NEW.id_driver)
FROM P p
WHERE (a.id = p.id_driver AND a.id=NEW.id_driver));
ELSIF TG_OP = 'DELETE' THEN
UPDATE A a
SET num_cars = num_cars - 1
WHERE a.id = OLD.id_driver AND a.num_cars<>0;
END IF;
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER add_car
AFTER INSERT OR DELETE ON PARTICIPATION
FOR EACH ROW EXECUTE PROCEDURE update_a();
The trigger works fine when I add a row in B for a driver. However, if I then add a row for a different driver in B the rest of the rows in A are set back to 0. I would like the procedure to run only when A.id = P.id_driver. How can I do this?
postgresql postgresql-9.1 postgresql-9.3
postgresql postgresql-9.1 postgresql-9.3
asked Nov 20 at 12:54
Sergio
164
asked Nov 20 at 12:54
Sergio
164
edited Nov 20 at 15:29
asked Nov 20 at 12:54
Sergio
164
asked Nov 20 at 12:54
Sergio
164
asked Nov 20 at 12:54
Sergio
164
164
Maybe because you're callingupdate_carin your trigger and notupdate_aor is that a typo?
– Joakim Danielson
Nov 20 at 13:33
I've corrected the typo, sorry for the confusion
– Sergio
Nov 20 at 15:29
add a comment |
Maybe because you're callingupdate_carin your trigger and notupdate_aor is that a typo?
– Joakim Danielson
Nov 20 at 13:33
I've corrected the typo, sorry for the confusion
– Sergio
Nov 20 at 15:29
Maybe because you're calling
update_car in your trigger and not update_a or is that a typo?– Joakim Danielson
Nov 20 at 13:33
Maybe because you're calling
update_car in your trigger and not update_a or is that a typo?– Joakim Danielson
Nov 20 at 13:33
I've corrected the typo, sorry for the confusion
– Sergio
Nov 20 at 15:29
I've corrected the typo, sorry for the confusion
– Sergio
Nov 20 at 15:29
add a comment |
1 Answer
1
active
oldest
votes
up vote
1
down vote
accepted
The update query makes a cross product between A and P, and therefore updates the entire table, counting 0 cars most of the time.
You would need to restrict the update to the proper driver only, and also to compute the number of cars only for this driver:
UPDATE A a
SET num_cars = (SELECT COUNT(*)
FROM P p
WHERE p.id_driver = NEW.id_driver)
WHERE a.id = NEW.id_driver;
answered Nov 20 at 15:58
JGH
3,09341025
Thanks for your help JGH, now it works wonderfully!
– Sergio
Nov 20 at 18:03
I upvoted it, but my votes don't show because my account doesn't have enough points.
– Sergio
Nov 21 at 8:57
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
1
down vote
accepted
The update query makes a cross product between A and P, and therefore updates the entire table, counting 0 cars most of the time.
You would need to restrict the update to the proper driver only, and also to compute the number of cars only for this driver:
UPDATE A a
SET num_cars = (SELECT COUNT(*)
FROM P p
WHERE p.id_driver = NEW.id_driver)
WHERE a.id = NEW.id_driver;
answered Nov 20 at 15:58
JGH
3,09341025
Thanks for your help JGH, now it works wonderfully!
– Sergio
Nov 20 at 18:03
I upvoted it, but my votes don't show because my account doesn't have enough points.
– Sergio
Nov 21 at 8:57
add a comment |
up vote
1
down vote
accepted
The update query makes a cross product between A and P, and therefore updates the entire table, counting 0 cars most of the time.
You would need to restrict the update to the proper driver only, and also to compute the number of cars only for this driver:
UPDATE A a
SET num_cars = (SELECT COUNT(*)
FROM P p
WHERE p.id_driver = NEW.id_driver)
WHERE a.id = NEW.id_driver;
answered Nov 20 at 15:58
JGH
3,09341025
Thanks for your help JGH, now it works wonderfully!
– Sergio
Nov 20 at 18:03
I upvoted it, but my votes don't show because my account doesn't have enough points.
– Sergio
Nov 21 at 8:57
add a comment |
up vote
1
down vote
accepted
up vote
1
down vote
accepted
The update query makes a cross product between A and P, and therefore updates the entire table, counting 0 cars most of the time.
You would need to restrict the update to the proper driver only, and also to compute the number of cars only for this driver:
UPDATE A a
SET num_cars = (SELECT COUNT(*)
FROM P p
WHERE p.id_driver = NEW.id_driver)
WHERE a.id = NEW.id_driver;
answered Nov 20 at 15:58
JGH
3,09341025
The update query makes a cross product between A and P, and therefore updates the entire table, counting 0 cars most of the time.
You would need to restrict the update to the proper driver only, and also to compute the number of cars only for this driver:
UPDATE A a
SET num_cars = (SELECT COUNT(*)
FROM P p
WHERE p.id_driver = NEW.id_driver)
WHERE a.id = NEW.id_driver;
answered Nov 20 at 15:58
JGH
3,09341025
edited Nov 24 at 16:54
answered Nov 20 at 15:58
JGH
3,09341025
answered Nov 20 at 15:58
JGH
3,09341025
answered Nov 20 at 15:58
JGH
3,09341025
3,09341025
Thanks for your help JGH, now it works wonderfully!
– Sergio
Nov 20 at 18:03
I upvoted it, but my votes don't show because my account doesn't have enough points.
– Sergio
Nov 21 at 8:57
add a comment |
Thanks for your help JGH, now it works wonderfully!
– Sergio
Nov 20 at 18:03
I upvoted it, but my votes don't show because my account doesn't have enough points.
– Sergio
Nov 21 at 8:57
Thanks for your help JGH, now it works wonderfully!
– Sergio
Nov 20 at 18:03
Thanks for your help JGH, now it works wonderfully!
– Sergio
Nov 20 at 18:03
I upvoted it, but my votes don't show because my account doesn't have enough points.
– Sergio
Nov 21 at 8:57
I upvoted it, but my votes don't show because my account doesn't have enough points.
– Sergio
Nov 21 at 8:57
add a comment |
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Maybe because you're calling
update_carin your trigger and notupdate_aor is that a typo?– Joakim Danielson
Nov 20 at 13:33
I've corrected the typo, sorry for the confusion
– Sergio
Nov 20 at 15:29